System and Method for Coupling a Topside to a Floating Substructure

ABSTRACT

Systems and methods for coupling a topside to a fixed or floating substructure during float-over installation of the topside are disclosed. Some system embodiments include a first plate coupled to a leg of the substructure and a retaining wall coupled to the first plate and extending substantially normally therefrom, wherein the retaining wall and the first plate form a recess. The system embodiments further include a second plate disposed at an end of a leg of the topside, the second plate received within the recess and engaging the first plate, and a plurality of shims disposed between the second plate and the retaining wall, wherein the plurality of shims are configured to inhibit translational movement of the second plate relative to the first plate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. provisional application Ser. No.60/946,647 filed Jun. 27, 2007, and entitled “Big Foot and DockingProbe,” which is hereby incorporated herein by reference in its entiretyfor all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

Embodiments of the invention relate to systems and methods forinstalling a topside or deck on a substructure to form a fixed orfloating offshore platform. More particularly, embodiments of theinvention relate to a novel system and method for coupling the topsidewith the substructure during float-over installation of the topside.

Float-over installations offer opportunities to install heavy topsidesbeyond the lifting capacity of available crane vessels on offshoresubstructures located in remote areas. A float-over installationincludes four primary procedures. The first procedure involvestransporting the topside or deck to the offshore substructure.Typically, the topside is placed on a barge or heavy transport vesseland towed to the substructure.

The second procedure involves docking the transport barge to theinstalled substructure. The barge is maneuvered into the slot of thesubstructure, such that the topside is floated over and substantiallyaligned with the substructure. Once in the slot, mooring lines,sometimes in combination with a fendering system, are utilized tosuppress surge and sway motions of the barge. After the mooring linesare set, deballasting of the substructure commences.

The third procedure involves transferring the load of the topside fromthe barge to the substructure, and is a critical phase of the float-overinstallation. Deballasting of the substructure continues as thesubstructure rises toward the topside. Once the topside and thesubstructure reach close proximity, the two bodies may impact each otherrepeatedly due to wave action. Such impacts may damage the structureswhen the relative motion between the two bodies is not controlled. Asdeballasting of the substructure continues, the weight of the topside isgradually transferred from the barge to the substructure. After acritical fraction of the weight is transferred, the relative motionbetween the two bodies ceases. At that point, the two structures move asa single unit, and the possibility of damage due to hard impact iseliminated. Therefore, it is desirable to complete the load transfer upto the critical fraction as quickly as possible.

After the topside is fully supported by the substructure, the legs ofthe two structures are coupled by welding legs extending downward fromthe topside to legs extending upward from the substructure. To achievethe high quality welds required to withstand the harsh load regimes ofoffshore environments, proper alignment of the topside with thesubstructure during the float-over operation is critical.

The final procedure involves separating the barge from the topside, andis also a critical phase of the float-over installation. Thesubstructure is deballasted further until the topside separates from thebarge. At and immediately after separation, the relative motions betweenbarge and topside pose a danger of damage due to impact between thesebodies. That danger can be minimized by rapid separation of the bargeand the topside. To promote such rapid separation, the topside may besupported on the barge by a number of loadout shoes. At the appropriatetime, the loadout shoes are actuated to quickly collapse or retract,thereby providing rapid separation between the barge and the topside.These systems, however, have a propensity to malfunction and permit hardcontact between the loadout shoes and the topside. In any event, hardcontact between the barge and the topside may continue until thesubstructure is deballasted to provide sufficient separation between thebarge and the topside. After which point, the barge is towed from theinstallation site.

Thus, embodiments of the invention are directed to apparatus and methodsthat seek to overcome these and other limitations of the prior art.

SUMMARY OF THE PREFERRED EMBODIMENTS

A system and method for coupling a topside to a fixed or floatingsubstructure during float-over installation of the topside aredisclosed. Some systems embodiments include a first plate coupled to aleg of the substructure, a retaining wall coupled to the first plate,and a second plate disposed at an end of a leg of the topside. Theretaining wall extends substantially normally from the first plate, suchthat the retaining wall and the first plate form a recess. The secondplate is received within the recess and engages the first plate. Thesystem embodiments may further include a plurality of shims disposedbetween the second plate and the retaining wall, wherein the shims areconfigured to inhibit translational movement of the second platerelative to the first plate.

The system embodiments may further include a tensioning system. Thetensioning system includes a connector coupled to the first plate anddisposed within the second plate, wherein the second plate is annular.The tensioning member further includes a support plate coupled to thetopside, a rod extending between the connector and the support plate,and a securing device coupled to an end of the rod. The securing deviceis configured to apply a tension load to the rod.

Some method embodiments for coupling a topside to a fixed or floatingsubstructure during float-over installation of the topside includecoupling a receptacle to a leg of the substructure. The receptacleincludes a first plate coupled to the leg of the substructure and aretaining wall coupled to the first plate. The retaining wall extendssubstantially normally from the first plate, wherein the retaining walland the first plate form a recess. The method embodiments furtherinclude disposing a second plate at an end of a leg of the topside,receiving the second plate within the recess, wherein the second plateengages the first plate, and installing a plurality of shims between thesecond plate and the retaining wall. The plurality of shims areconfigured to inhibit translational movement of the second platerelative to the first plate.

Thus, the embodiments of the invention comprise a combination offeatures and advantages that enable substantial enhancement offloat-over installation systems and methods. These and various othercharacteristics and advantages of the invention will be readily apparentto those skilled in the art upon reading the following detaileddescription of the preferred embodiments of the invention and byreferring to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of the preferred embodiments of theinvention, reference will now be made to the accompanying drawings inwhich:

FIGS. 1A and 1B are cross-sectional and top views of weldless topsidecoupling system in accordance with embodiments of the invention;

FIG. 2 is a cross-sectional view of an installed substructure includingsome components of the coupling system of FIG. 1;

FIG. 3 is a cross-sectional view of a topside including the remainingcomponents of the coupling system of FIG. 1 floated over thesubstructure of FIG. 2;

FIG. 4 is a cross-sectional view of a tensioning member coupled betweena topside and a substructure; and

FIG. 5 is a cross-sectional view of a weldless coupling system andtensioning member coupled between the topside and the substructure ofFIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Various embodiments of the invention will now be described withreference to the accompanying drawings, wherein like reference numeralsare used for like parts throughout the several views. The drawingfigures are not necessarily to scale. Certain features of the inventionmay be shown exaggerated in scale or in somewhat schematic form, andsome details of conventional elements may not be shown in the interestof clarity and conciseness.

Preferred embodiments of the invention relate to a weldless system andmethod for coupling a topside with an installed substructure to form afixed or floating platform. The invention is susceptible to embodimentsof different forms. There are shown in the drawings, and herein will bedescribed in detail, specific embodiments of the invention with theunderstanding that the disclosure is to be considered an exemplificationof the principles of the invention and is not intended to limit theinvention to that illustrated and described herein. It is to be fullyrecognized that the different teachings of the embodiments discussedbelow may be employed separately or in any suitable combination toproduce desired results.

As described above during a conventional float-over installation of atopside on an installed substructure, the topside is floated over andsubstantially aligned with the substructure using a barge. Thesubstructure is then deballasted to engage and lift the topside from thebarge, thereby assembling the fixed or floating platform. The topside isthen coupled to the substructure by welding. Embodiments of theinvention are directed to a system and method for coupling the topsideto the substructure without the need for precise alignment of thetopside relative to the substructure and subsequent welding.

FIGS. 1A and 1B depict representative cross-sectional and top views,respectively, of a topside or deck installed via float-over on arepresentative cross-section of a substructure 105 for asemi-submersible offshore platform, such as a multicolumn floating (MCF)platform. More specifically, a leg 110 of the topside is shown coupledto a leg 115 of the substructure by a weldless topside coupling system120. Coupling system 120 includes an annular plate 125 disposed at thelower end 130 of leg 110. In this exemplary embodiment, plate 125 isformed separately from leg 110 and then coupled to leg 110 as shown. Inother embodiments, however, plate 125 may be formed integrally with leg110. After the topside is landed on the substructure, as shown, leg 115of the substructure supports leg 110 of the topside. By disposingannular plate 125 at end 130 of leg 110, the area or footprint of leg110 in contact with leg 115 is significantly increased, in comparison tothe footprint of leg 110 that would otherwise contact leg 115 in theabsence of plate 125. Because annular plate 125 increases the footprintof leg 110, annular plate 125 is also referred to the big foot.

Weldless coupling system 120 further includes a receptacle or bucket 135disposed at the upper end 140 of leg 115. Bucket 135 includes a baseplate 145 having an upper surface 155 and a retaining wall 150 coupledthereto. Retaining wall 150 extends substantially normally upward fromupper surface 155. As shown in FIG. 1B, retaining wall 150 is generallycircular in shape. Further, the inner envelope of retaining wall 150 isselected such that annular plate 125 may be received therein.

For additional support, one or more small gusset plates 160 are coupledto bucket 135 between upper surface 155 of base plate 145 and the outersurface 165 of retaining wall 150. Plates 160 provide support toretaining wall 150 when lateral force is applied to the inner surface170 of wall 150, where the lateral direction is substantially parallelto base plate 145. Also for additional support, one or more large gussetplates 175 are coupled to bucket 135 between the lower surface 180 ofbase plate 145 and the outer surface 185 of leg 115. Plates 175 providesupport to base plate 145 when an asymmetric vertical load, definedrelative to a longitudinal centerline 190 through leg 115, is applied toupper surface 155 of base plate 145.

In some embodiments, weldless coupling system 120 further includes twoor more pairs of tapered or wedge-shaped shims 200 disposed on uppersurface 155 of base plate 145 between the outer surface 205 of plate 125and inner surface 170 of retaining wall 150. When installed, shims 200prevent translational movement of plate 125 relative to base plate 145,and thus lateral movement of leg 110 relative to leg 115. In at leastsome embodiments, shims 200 are formed of steel. Each pair of shims 200comprises an inner shim 210 proximate plate 125 and an adjacent outershim 215 proximate retaining wall 150. The adjacent surfaces of innershim 210 and outer shim 215 form a non-slip taper 220 configured toprevent sliding of shims 210, 215 relative to each other.

Weldless coupling system 120 may further include a coating 225 disposedbetween retaining wall 150 and plate 125 and covering shims 200. Coating225 is configured to prevent corrosion of shims 200 and potentialslippage of inner shims 210 relative to outer shims 215. Coating 225 mayinclude an epoxy resin material, such as chalk-fast, tar, or otherequivalent material known in the art.

Alternatively, weldless coupling system 120 may include a hardenablematerial 455 (FIG. 5) in place of shims 200 and coating layer 225, ifpresent. Hardenable material 455 is disposed within bucket 135surrounding and covering plate 125. Further, hardenable material 455 isapplied in liquid form but subsequently hardens into solid form. Likeshims 200, material 455, once hardened, prevents slippage of plate 125relative to base plate 145, and thus lateral movement of leg 110relative to leg 115. Hardenable material 455 may include a grout, epoxyresin, or other equivalent material.

With the exception of shims 200, coating layer 225 and hardenablematerial 455, components of docking system 110 are coupled to leg 110 ofthe topside or leg 115 of the substructure, as appropriate, prior totransport of the topside and the substructure to the desired offshoreinstallation site. Bucket 135 and plates 160, 175 are coupled to leg 115of the substructure, for example, by welding. Similarly, annular plate125, if formed separately from leg 110, is coupled to leg 110, forexample, by welding.

The substructure, with leg 115 and components of weldless couplingsystem 120 coupled thereto, is then towed to the installation site, asshown in FIG. 2. Upon reaching the installation site, the substructure105 is ballasted to the desired depth. The topside 100, with leg 110 andcomponents of weldless coupling system 120 coupled thereto, is nexttowed to and floated over substructure 105 by a barge 107, as previouslydescribed and shown in FIG. 3.

After topside 100 is aligned over substructure 105, substructure 105 isdeballasted to engage topside 100. More particularly, substructure 105is deballasted to allow bucket 135, coupled to upper end 140 of leg 115,to receive annular plate 125, coupled to lower end 130 of leg 110, suchthat plate 125 lands on upper surface 155 of base plate 145 withinretaining wall 150, as shown in FIG. 1A. Continued deballasting ofsubstructure 105 enables load transfer of topside 100 from barge 107 tosubstructure 105. In other words, substructure 105 begins to lifttopside 100 from barge 107.

When the load of topside 100 is completely supported by substructure105, shims 200 may then hammered into position between annular plate 120and retaining wall 150. Once installed, shims 200 prevent subsequentsliding of plate 125, and leg 110 coupled thereto, relative to bucket135, and leg 115 coupled thereto. Lateral loads exerted by leg 110 inresponse to the surrounding water are instead transferred through shims200 to retaining wall 150, which resists these loads with support fromgusset plates 160. If desired, coating 225 is then applied between plate125 and retaining wall 150 to cover shims 200. Alternatively, hardenablematerial 455 may be applied to fill bucket 135 and cover plate 125 andallowed to harden. Finally, barge 107 is released from topside 100.

Weldless coupling system 120 does not require welding to couple thetopside to the substructure. Analysis has shown that welding isunnecessary because the dynamic motions of the substructure, even duringexpected hurricane conditions, will not cause plate 125 to separate orlift off of bucket 135 due to the weight of installed topside 100.Further, when weldless coupling system 120 is utilized to couple atopside to a substructure, precise alignment of the topside prior todeballasting the substructure to engage and lift the topside is alsounnecessary for a number of reasons. For one, the topside will not bewelded to the substructure once engaged. Also, bucket 135 provides asignificantly increased area upon which leg 110 may land, relative tothat available during conventional float-over procedures in the absenceof coupling system 120. Thus, the topside may be misaligned to a degreeand leg 110 will still land within the inner envelope of bucket 135 asthe substructure is deballasted. Further, the structural integrity ofbase plate 145 in combination with support from gusset plates 175 iscapable of supporting leg 110 with annular plate 125 coupled thereto ofwithstanding asymmetric vertical loading, such as those resulting whenleg 110 lands within bucket 135 off-center of centerline 190 of leg 115.Similarly, annular plate 125 is also capable of withstanding asymmetricvertical loading resulting from off-center engagement of plate 125 withbucket 135.

If desired, weldless coupling system 120 may be supplemented with apositive tie-down means coupled between topside 100 and substructure 105in case of an unforeseen extreme event, such as an atypical hurricane oran earthquake. For example, and referring now to FIG. 4, one or moretensioning members 400 may be coupled between topside 100 andsubstructure 105, as shown. Tensioning member 400 includes a supportplate 405, a connector 410 and a tie rod 415 extending therebetween.Support plate 405 is coupled to an upper surface 420 of topside 100.Support plate 405 includes a throughbore 435 configured to receive theupper end 440 of tie rod 415. Connector 410 is coupled to an uppersurface 430 of substructure 105. Tie rod 415 is coupled to connector 410and extends upward through throughbore 435 of support plate 405. In someembodiments, tie rod 415 extends within a deck column member 425, asshown. Upper end 440 of tie rod 415 is coupled to support plate 405 by atensioning and securing device 445 seated on plate 405. Device 445 isconfigured to apply a tension load to tie rod 415.

Like those of coupling system 120, components of tensioning member 400are coupled to topside 100 or substructure 105, as appropriate, prior totransport of topside 100 and substructure 105 to the desired offshoreinstallation site. After topside 100 is landed on substructure 105 asdescribed above, meaning leg 110 of topside 100 with plate 125 theretois landed within bucket 135 coupled to leg 115 of substructure 105, tierod 415 is inserted through throughbore 435 of support plate 405 andlowered to engage connector 410. Securing and tensioning device 445 isthen disposed over upper end 440 of tie rod 415 and seated on supportplate 405. Device 445 is next operated to apply a tension load to tierod 415. Once tie rod 415 is tensioned to the desired load, installationof tensioning member 400 is complete.

In some embodiments, tensioning member 400 may be installed between legs110, 115 of topside 100 and substructure 105, respectively, coupledusing weldless topside coupling system 120, shown and described abovewith reference to FIGS. 1-3. In such embodiments, connector 410 oftensioning member 400 is coupled to upper surface 155 of base plate 145of weldless coupling system 120, as shown in FIG. 5. Also, support plate405 of tensioning member 400 is coupled to an upper surface 115 oftopside 100 from which leg 110 extends. Otherwise, the remainingcomponents of tensioning member 400 are positioned and installed asdescribed above in reference to FIG. 4.

While preferred embodiments have been shown and described, modificationsthereof can be made by one skilled in the art without departing from thescope or teachings herein. The embodiments described herein areexemplary only and are not limiting. Many variations and modificationsof the systems are possible and are within the scope of the invention.For example, the relative dimensions of various parts, the materialsfrom which the various parts are made, and other parameters can bevaried. Accordingly, the scope of protection is not limited to theembodiments described herein, but is only limited by the claims thatfollow, the scope of which shall include all equivalents of the subjectmatter of the claims.

1. A system for coupling a topside to a substructure during float-over installation of the topside, the system comprising: a first plate coupled to a leg of the substructure; a retaining wall coupled to the first plate and extending substantially normally therefrom, wherein the retaining wall and the first plate form a recess; and a second plate disposed at an end of a leg of the topside, the second plate received within the recess and engaging the first plate.
 2. The system of claim 1, wherein the second plate is annular.
 3. The system of claim 1, wherein the second plate has a lower surface in contact with the first plate and wherein the topside leg has a cross-section substantially parallel to the second plate, wherein the lower surface in contact with the first plate has an area greater than the area of the cross-section.
 4. The system of claim 1, further comprising a plurality of shims disposed between the second plate and the retaining wall, wherein the plurality of shims are configured to inhibit translational movement of the second plate relative to the first plate.
 5. The system of claim 4, wherein the plurality of shims comprises: a first plurality of inner shims, each inner shim positioned adjacent the second plate; and an equal number of outer shims, each outer shim positioned between one of the first plurality of inner shims and the retaining wall.
 6. The system of claim 5, wherein each inner shim comprises an outer surface in contact with an inner surface of the adjacent outer shim, wherein the outer surface of each inner shim and the inner surface of each outer shim are configured to resist translational movement relative to one another.
 7. The system of claim 6, wherein the inner surface of each outer shim and the outer surface of each adjacent inner shim are tapered.
 8. The system of claim 4, further comprising a coating layer covering the plurality of shims.
 9. The system of claim 8, wherein the coating layer comprises one of the group consisting of epoxy resin and tar.
 10. The system of claim 1, further comprising a hardenable material layer disposed between the retaining wall and the second plate.
 11. The system of claim 10, wherein the hardenable material layer comprises one of the group consisting of epoxy resin and gout.
 12. The system of claim 1, wherein the retaining wall is circular.
 13. The system of claim 1, further comprising a plurality of gusset plates disposed circumferentially around the retaining wall and extending substantially normally therefrom, wherein each gusset plate is coupled to the retaining wall and the first plate.
 14. The system of claim 1, further comprising a plurality of gusset plates disposed circumferentially around the leg of the substructure and extending substantially normally therefrom, wherein each gusset plate is coupled to the leg of the substructure and the first plate.
 15. A system for coupling a topside to a substructure during float-over installation of the topside, the system comprising: a coupling system comprising: a solid plate coupled to a leg of the substructure; a retaining wall coupled to the solid plate and extending substantially normally therefrom, wherein the retaining wall and the solid plate form a recess; and an annular plate disposed at an end of a leg of the topside, the annular plate received within the recess and engaging the solid plate; and a tensioning system comprising: a connector coupled to the solid plate; a support plate coupled to the topside; a rod extending between the connector and the support plate; and a securing device coupled to an end of the rod, the securing device configured to apply a tension load to the rod.
 16. The system of claim 15, wherein the connector is coupled to the solid plate and disposed within the annular plate.
 17. The system of claim 15, wherein the annular plate has a lower surface in contact with the solid plate and wherein the topside leg has a cross-section substantially parallel to the annular plate, wherein the lower surface in contact with the solid plate has an area greater than the area of the cross-section.
 18. The system of claim 15, further comprising a plurality of shims disposed between the second plate and the retaining wall, wherein the plurality of shims are configured to inhibit translational movement of the annular plate relative to the solid plate.
 19. The system of claim 18, wherein the plurality of shims comprises: a first plurality of inner shims, each inner shim positioned adjacent the second plate; and an equal number of outer shims, each outer shim positioned between one of the first plurality of inner shims and the retaining wall; wherein each inner shim comprises an outer surface in contact with an inner surface of the adjacent outer shim, wherein the outer surface of each inner shim and the inner surface of each outer shim are configured to resist translational movement relative to one another.
 20. The system of claim 15, further comprising a hardenable material layer disposed between the retaining wall and the annular plate.
 21. The system of claim 15, further comprising a plurality of gusset plates disposed circumferentially around the retaining wall and extending substantially normally therefrom, wherein each gusset plate is coupled to the retaining wall and the first plate.
 22. The system of claim 15, further comprising a plurality of gusset plates disposed circumferentially around the leg of the substructure and extending substantially normally therefrom, wherein each gusset plate is coupled to the leg of the substructure and the first plate.
 23. The system of claim 15, further comprising a coating layer covering the plurality of shims.
 24. A method for coupling a topside to a substructure during float-over installation of the topside, the method comprising: coupling a receptacle to a leg of the substructure, the receptacle comprising: a first plate coupled to the leg of the substructure; and a retaining wall coupled to the first plate, the retaining wall extending substantially normally therefrom; wherein the retaining wall and the first plate form a recess; disposing a second plate at an end of a leg of the topside; and receiving the second plate within the recess, wherein the second plate engages the first plate.
 25. The method of claim 24, further comprising installing a plurality of shims between the second plate and the retaining wall, wherein the plurality of shims are configured to inhibit translational movement of the second plate relative to the first plate.
 26. The method of claim 25, further comprising covering the plurality of shims with a coating layer.
 27. The method of claim 24, wherein the receiving comprises deballasting the substructure to position the second plate within the recess and in engagement with the first plate.
 28. The method of claim 24, further comprising coupling a first plurality of gusset plate between an outer surface of the retaining wall and the first plate and coupling a second plurality of gusset plates between an outer surface of the leg of the substructure and the first plate.
 29. The method of claim 24, further comprising applying a hardenable material layer between the retaining wall and the second plate. 